Solid-state image capturing device, smear charge removing method and digital still camera using the same

ABSTRACT

In a solid-state image capturing device including a pixel array arranged in a row direction and a column direction orthogonal thereto, and a vertical register having a plurality of transfer electrodes which serves to read signal charges Qa, Qb, . . . generated by light receipt of each of pixels A, B, . . . and to sequentially transfer the signal charge in the column direction upon receipt of a transfer pulse, an electric potential well for a smear charge is generated and an unnecessary charge q in the vertical register is collected into the electric potential well for a smear charge before the signal charge is read from the pixels A, B, . . . onto the vertical register (a timing t 707 ), an electric potential well for signal charge transfer is then generated and the signal charges Qa, Qb, . . . are read from the pixels A, B, . . . onto the electric potential well for signal charge transfer, and the electric potential well for a smear charge and the electric potential well for signal charge transfer are transferred in the direction of a horizontal register without mixing an unnecessary charge  3   q  with a signal charge Q.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application of co-pending application Ser. No.10/329,795, filed Dec. 27, 2002, which is a non-provisional applicationthat claims priority under 35 U.S.C. §119 on Patent Application No.2001-399713 filed in Japan on Dec. 28, 2001, the entire contents of allof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital still camera having anelectronic shutter function, and more particularly to a solid-stateimage capturing device capable of acquiring a captured image which isnot influenced by a smear when releasing a high-speed shutter tocapturing an image by the electronic shutter function, a smear chargeremoving method and a digital still camera.

2. Description of the Related Art

FIG. 18 is a schematic plan view showing a conventional solid-stateimage capturing device having pixels arranged like a square grid. In asolid-state image capturing device 10, a photoreceptor group includes aphotoreceptor 11 b having a blue filter attached thereto and aphotoreceptor 11 g having a green filter attached thereto which arealternately arranged in a transverse row and a photoreceptor groupincludes the photoreceptor 11 g having the green filter attached theretoand a photoreceptor 11 r having a red filter attached thereto which arealternately arranged in a transverse row, and both of the groups arealternately arranged in a vertical direction.

A transfer electrode 16 is provided around each of the photoreceptors 11r, 11 g and 11 b, and a transfer electrode group in a vertical columnwhich is constituted by the transfer electrode 16 forms a vertical CCDregister 12 (only one column is shown in a dotted line). A firsttransfer electrode 16 group in a transverse row which is arranged in theupper side portions of the photoreceptors 11 r, 11 g and 11 b isconnected to an electrode terminal 21, a second transfer electrode 16group in a transverse row which is arranged in the lower side portionsof the photoreceptors 11 r, 11 g and 11 b is connected to an electrodeterminal 22, and a third transfer electrode 16 group in a transverse rowwhich is provided between a photoreceptor group arranged in a transversecolumn and a photoreceptor group arranged in a next transverse row isconnected to an electrode terminal 23.

When a reading potential is applied to a reading gate which is not shownin order to read image signals picked up by the solid-state imagecapturing device 10 (the received charges of the photoreceptors 11 r, 11g and 11 b), the received charges (signal charges) of the photoreceptors11 r, 11 g and 11 b are read onto the transfer electrode 16 of thevertical CCD register 12 as shown in an arrow on each of thephotoreceptors 11 r, 11 g and 11 b.

A transfer potential (a transfer pulse) is sequentially applied to eachof the electrode terminals 21 to 23 so that a received charge istransferred in a vertical direction (a downward direction in the exampleshown in the drawing) and a signal charge is transferred to a horizontalregister 13 provided in the lowest stage. The signal charge istransferred in a horizontal direction by the application of the transferpulse to electrode terminals 25 and 26 and is output from an outputsection 14 of the horizontal register 13. Moreover, the solid-stateimage capturing device 10 is provided with an electrode terminal 28 forOFD pulse application which will be described below.

FIG. 19 is a diagram showing the operation timing of a digital stillcamera mounting a mechanical shutter and the conventional solid-stateimage capturing device. In the case in which a shutter button is notreleased in the digital still camera, a captured image (a dynamic image)is displayed on the LCD display section at the back face of the camerato serve as a finder. Therefore, a vertical blanking pulse is generatedat an interval of 1/30 to 1/60 second and a captured image signal isfetched every 1/30 to 1/60 second, for example.

When the shutter button is released (ON), a time interval betweensubsequent vertical blanking pulses is set to be 1/10 second, forexample, and a static image is fetched with each of reading pulses B1,B2, generated in vertical blanking pulses A1, A2, . . . .

However, the image signal fetched with the first reading pulse B1 iscancelled as a dummy output and the image signal fetched with the nextreading pulse B2 is output as the image signals of a static image.Moreover, an OFD (overflow drain) pulse is applied after the firstvertical blanking pulse A1, and the stored charges of the photoreceptors11 r, 11 g and 11 b formed on the surface of the semiconductor substrateof the solid-state image capturing device are drained toward the backside of the semiconductor substrate, and the stored charges of thephotoreceptors 11 r, 11 g and 11 b are zero cleared before the start ofthe image capturing.

Moreover, the transfer pulse (FIG. 19 shows only a second-phase transferpulse VP2 and a change in an ON/OFF state is omitted in cross-hatching)which is applied from the electrode terminals 21, 22 and 23 to thevertical CCD register 12 is transmitted at a high speed immediatelyafter the rise of the next vertical blanking pulse A2 till the rise ofthe reading pulse B2 (a blackened portion X in the drawing), and theelectric charge in the vertical CCD register 12 is swept at a high speedbefore the signal charge of image information is fetched from thephotoreceptors 11 r, 11 g and 11 b into the vertical CCD register 12.

After the application of the OFD pulse till the closing of themechanical shutter, the signal charges stored in the photoreceptors 11r, 11 g and 11 b are read and transferred to the vertical CCD register12, and are output as the signals of a static image.

FIG. 20 is a timing chart for explaining the transfer state of thevertical CCD register 12 in the solid-state image capturing device 10shown in FIG. 18. In the drawing, an encircled figure represents a lastone digit of the designation of each of the electrode terminals 21 to23. By cyclically applying a transfer potential (for example, pulseshaving a high level (0 V) and a low level (−8 V) to each electrodeterminal, an electric potential well is moved along the vertical CCDregister 12 and signal charges Qsiga, Qsigb, . . . constituting theimage signals are transferred to the horizontal register 13.

At this time, light or an electron leaks from the photoreceptors 11 r,11 g and 11 b into the vertical CCD register 12 also before the receivedcharges of pixels A, B, C . . . (the photoreceptors 11 r, 11 g and 11 b)are read onto the vertical CCD register 12, and the original signalcharges Qsiga, Qsigb, . . . , and furthermore, a smear charge qsmrcausing a smear (a bright line in a longitudinal direction which appearsin an image when the sun is photographed) enters each electric potentialwell.

As described above, a high-speed sweeping pulse X is applied to thevertical CCD register 12 in timings t8 to t9 of FIG. 19, and the smearcharge qsmr is swept completely to cause each electric potential well tobe completely empty (timing t9), and the signal charges Qsiga, Qsigb, .. . of the pixels A, B, . . . are then read (timing t10) and aretransferred to the horizontal register 13. Consequently, it is possibleto obtain an excellent image having no smear.

However, the operation timing of the digital still camera is illustratedin FIG. 19 as an example of a low-speed shutter using a mechanicalshutter. While the vertical CCD register 12 is being driven by thesweeping pulse X, the mechanical shutter is maintained in a closingstate. Therefore, there is no possibility that a new smear charge mightenter the electric potential well.

On the other hand, in the case in which an image is to be picked up by ahigh-speed shutter, the mechanical shutter cannot release the high-speedshutter. As shown in FIG. 21, therefore, the high-speed shutter isreleased by the electronic shutter function. In this case, a period fromthe timing t6 immediately after the OFD pulse to the timing t8 of thereading pulse B2 is set to be a shutter time in a state in which themechanical shutter is opened, and the signal charges stored in thephotoreceptors 11 r, 11 g and 11 b are read as the signals of capturedimages in the shutter time.

Also in this case, the smear charge in the vertical CCD register 12 isswept by the sweeping pulse X before the reading pulse B2 and thesweeping is carried out in a state in which the mechanical shutter isopened. Therefore, the smear charge qsmr enters the electric potentialwell during the sweeping.

In the case in which the high-speed shutter is released by theelectronic shutter function, accordingly, smear charges qi+1, qi, . . .enter the electric potential well for transferring the signal chargesQsiga, Qsigb, . . . as shown in FIG. 22 so that the same smear chargesare transferred together with the signal charges. The smear chargesqi+1, qi, . . . cannot be distinguished from the signal charges Qsiga,Qsigb, . . . . For this reason, the picture quality of the capturedimage is deteriorated.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a solid-state imagecapturing device capable of picking up an image which is not influencedby a smear even if a high-speed shutter is released by the electronicshutter function, a smear charge removing method and a digital stillcamera.

The object can be attained by a solid-state image capturing deviceincluding a pixel array arranged in a row direction and a columndirection orthogonal thereto, a vertical register having a plurality oftransfer electrodes which serves to read a signal charge generated bylight receipt of each pixel and to sequentially transfer the signalcharge in the column direction upon receipt of a transfer pulse, ahorizontal register for receiving the signal charge transferred by thevertical register and transmitting the signal charge in a horizontaldirection, and an output section for outputting the signal chargetransferred by the horizontal register, the solid-state image capturingdevice comprising means for generating an electric potential well for asmear charge and collecting an unnecessary charge in the verticalregister into the electric potential well for a smear charge beforereading the signal charge from the pixel onto the vertical register,means for generating an electric potential well for signal chargetransfer after collecting the unnecessary charge into the electricpotential well for a smear charge and reading the signal charge from thepixel onto the electric potential well for signal charge transfer, andmeans for transferring the electric potential well for a smear chargeand the electric potential well for signal charge transfer to thehorizontal register without mixing the unnecessary charge with thesignal charge. By such a structure, the smear charge is not mixed withthe signal charge so that an excellent image having no smear can beobtained.

In the foregoing, it is preferable that there should be providedselecting means for switching a first mode for generating the electricpotential well for a smear charge and transferring the signal charge bythe vertical register and a second mode for transferring the signalcharge by the vertical register without generating the electricpotential well for a smear charge. By such a structure, in the case inwhich the cancellation of the smear charge is not required, the signalcharge is transferred without providing the electric potential well fora smear charge. Therefore, high-speed transfer can be carried out.

In the foregoing, it is preferable that the solid-state image capturingdevice should be an interline transfer type CCD area image sensor or aframe interline transfer type CCD area image sensor, and furthermore,the pixel array should be arranged like a square grid or a honeycomb.The invention can be applied irrespective of the type of the CCD imagesensor.

In the foregoing, it is further preferable that there should be providedmeans for distinguishing a voltage signal based on the unnecessarycharge transferred by the electric potential well for a smear chargefrom a voltage signal based on the signal charge and outputting thevoltage signal. By such a structure, the image signal can bedistinguished from the smear signal by a signal processing circuit inthe second stage of the solid-state image capturing device.

In the foregoing, it is further preferable that there should be provideddischarge means for discharging the unnecessary charge transferred bythe electric potential well for a smear charge in the solid-state imagecapturing device, and furthermore, the discharge means should beprovided in a connecting portion of the vertical register and thehorizontal register or at an output end of the horizontal register. Bysuch a structure, it is possible to relieve the load of a signalprocessing in the second stage of the solid-state image capturingdevice.

In the foregoing, it is further preferable that there should be providedmeans for driving the vertical register with a high-speed pulse beforecollecting the unnecessary charge into the electric potential well for asmear charge and sweeping the unnecessary charge. By such a structure,it is possible to reduce the quantity of unnecessary charges collectedin the electric potential well for a smear charge.

In order to attain the object, a smear charge removing method comprisesthe steps of generating an electric potential well for a smear chargebefore reading a signal charge picked up by the solid-state imagecapturing device and stored in a pixel onto a vertical register andcollecting an unnecessary charge in the vertical register into theelectric potential well for a smear charge, generating an electricpotential well for signal charge transfer and reading the signal chargefrom the pixel onto the electric potential well for signal chargetransfer, and transferring the electric potential well for a smearcharge and the electric potential well for signal charge transfer to ahorizontal register without mixing the unnecessary charge with thesignal charge. By such a structure, it is possible to obtain an image inwhich a deterioration in picture quality is not caused by the smear.

In the foregoing, it is further preferable that the unnecessary chargetransferred by the electric potential well for a smear charge should becancelled in the solid-state image capturing device. By such astructure, it is possible to relieve the signal processing load in thesecond stage of the solid-state image capturing device.

In order to attain the object, a digital still camera comprises thesolid-state image capturing device described above, an optical systemfor forming an image of an object in the solid-state image capturingdevice, a signal processing section for processing a signal output fromthe output section of the solid-state image capturing device andgenerating an image, and a memory section for recording the image thusgenerated. By such a structure, it is possible to capturing an excellentimage having no smear even if a high-speed shutter is released by theelectronic shutter function.

In order to achieve the object, a digital still camera comprises thesolid-state image capturing device described above, an optical systemfor forming an image of an object in the solid-state image capturingdevice, a mechanical shutter for shielding the optical system, a signalprocessing section for processing a signal output from the outputsection of the solid-state image capturing device and generating animage, a memory section for recording the image thus generated, andcontrol means for transferring a signal charge obtained by lightshielding using the mechanical shutter into the solid-state imagecapturing device and outputting the signal charge from the solid-stateimage capturing device without generating the electric potential wellfor a smear charge, and for generating the electric potential well for asmear charge when obtaining the signal charge by an electronic shutterwithout using the mechanical shutter, transferring the electricpotential well for a smear charge into the solid-state image capturingdevice and outputting the electric potential well for a smear chargefrom the solid-state image capturing device.

By such a structure, the smear charge is canceled when the high-speedshutter is released by an electronic shutter, and the cancellation ofthe smear charge is not required when the mechanical shutter isreleased. Consequently, it is possible to generate an image withoutremoving the smear charge.

In the foregoing, it is preferable that there should be provided meansfor superposing, synthesizing and outputting a static image signalobtained by picking up an image without using the mechanical shutter anda static image signal obtained by picking up an image using themechanical shutter continuously with the image capturing. By such astructure, it is possible to capturing a static image having a widedynamic range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the structure of a digital still cameraaccording to an embodiment of the invention,

FIG. 2 is a schematic plan view showing a solid-state image capturingdevice according to a first embodiment of the invention,

FIG. 3 is a timing chart for explaining a transfer method in thesolid-state image capturing device shown in FIG. 2,

FIG. 4 is a timing chart which is connected to FIG. 3,

FIG. 5 is a schematic plan view showing a solid-state image capturingdevice according to a second embodiment of the invention,

FIG. 6 is a diagram showing the operation timing of the solid-stateimage capturing device illustrated in FIG. 5,

FIG. 7 is a timing chart for explaining a transfer method in thesolid-state image capturing device shown in FIG. 5,

FIG. 8 is a timing chart for explaining a transfer method in asolid-state image capturing device according to a third embodiment ofthe invention,

FIG. 9 is a schematic plan view showing a solid-state image capturingdevice according to a fourth embodiment of the invention,

FIG. 10 is a timing chart for explaining a transfer method in thesolid-state image capturing device shown in FIG. 9,

FIG. 11 is a schematic plan view showing a solid-state image capturingdevice according to a fifth embodiment of the invention,

FIG. 12 is a timing chart for explaining a transfer method in thesolid-state image capturing device shown in FIG. 11,

FIG. 13 is a timing chart connected to FIG. 12,

FIG. 14 is a diagram showing the structure of a digital still cameraaccording to another embodiment of the invention,

FIG. 15 is a diagram showing the operation timing of the digital stillcamera illustrated in FIG. 14,

FIGS. 16( a) and 16(b) show the illustrations of a structure in which asmear charge transferred in the embodiment of the invention isdischarged through an end of a vertical CCD register,

FIG. 17 is a view illustrating a structure in which the smear chargetransferred in the embodiment of the invention is discharged through ahorizontal CCD register,

FIG. 18 is a schematic plan view showing a conventional solid-stateimage capturing device,

FIG. 19 is a diagram showing an operation timing for obtaining an imagepicked up by a low-speed shutter in the solid-state image capturingdevice illustrated in FIG. 18,

FIG. 20 is a timing chart for explaining a transfer method in thesolid-state image capturing device shown in FIG. 18,

FIG. 21 is a diagram showing an operation timing for obtaining an imagepicked up by a high-speed shutter in the solid-state image capturingdevice illustrated in FIG. 18, and

FIG. 22 is a view for explaining a problem in the solid-state imagecapturing device shown in FIG. 18.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will be described below with reference tothe drawings.

FIG. 1 is a diagram showing the structure of a digital still cameraaccording to the embodiment of the invention. The digital still cameracomprises a solid-state image capturing device 30, an optical system 31for forming the image of an object in the solid-state image capturingdevice 30, a mechanical shutter 32 provided between the solid-stateimage capturing device 30 and the optical system 31, a drive circuit 33for driving the solid-state image capturing device 30, an analog/digitalconverting section 34 for converting an analog image signal read fromthe solid-state image capturing device 30 into a digital image signal, asignal processing section 35 for processing a digital image signal, arecording section 36 for storing the image signal thus processed, aliquid crystal display section 37 provided on the back face of a digitalcamera, used in place of a finder and capable of displaying a capturedimage, and a control section 38 for controlling the drive circuit 33,the signal processing section 35 and the recording section 36.

The signal processing section 35 comprises a switch 35 a for switchingthe output destination of the digital image signal output from theanalog/digital converting section 34, a dynamic image processing section35 b for processing, into a dynamic image, the digital image signalfetched through the switch 35 a, a static image processing section 35 cfor processing, into a static image, the digital image signal fetchedthrough the switch 35 a, and a common signal processing section 35 d forreceiving the results of the processings of the dynamic image processingsection 35 b and the static image processing section 35 c and carryingout another image processing.

FIG. 2 is a schematic plan view showing a solid-state image capturingdevice according to a first embodiment of the invention. In thesolid-state image capturing device 30, a photoreceptor group includes aphotoreceptor 11 b having a blue filter attached thereto and aphotoreceptor 11 g having a green filter attached thereto which arealternately arranged in a transverse row and a photoreceptor groupincludes the photoreceptor 11 g having the green filter attached theretoand a photoreceptor 11 r having a red filter attached thereto which arealternately arranged in a transverse row, and both of the groups arealternately arranged in a vertical direction. Each of the photoreceptors11 r, 11 g and 11 b is arranged like a square grid.

A transfer electrode 16 is provided around each of the photoreceptors 11r, 11 g and 11 b, and a transfer electrode group in a vertical columnwhich is constituted by the transfer electrode 16 forms a vertical CCDregister 12 (only one column is shown in a dotted line). Hereinafter,one column in a transverse direction will be referred to as a “row” andone column in a vertical direction will be referred to as a “column”.

The conventional solid-state image capturing device 10 described withreference to FIG. 18 is provided the three electrode terminals 21, 22and 23 in order to 3-phase drive the vertical CCD register 12. In thesolid-state image capturing device 30 according to the embodiment, nineelectrode terminals 301 to 309 are provided in order to 9-phase drivethe vertical CCD register 12.

In the transfer electrode 16, a transfer electrode 16 group in atransverse row which is arranged in the upper side portion of thephotoreceptor group in a first row is connected to an electrode terminal301, a transfer electrode 16 group in a transverse column which isarranged in the lower side portion of the photoreceptor group in thefirst row is connected to an electrode terminal 302, and a transferelectrode 16 group in a transverse row which is provided between thephotoreceptor group in the first row and the a photoreceptor group in asecond row is connected to an electrode terminal 303.

Furthermore, a transfer electrode 16 group in a transverse row which isarranged in the upper side portion of the photoreceptor group in thesecond row is connected to an electrode terminal 304, and so forth, anda transfer electrode 16 group in a transverse row which is providedbetween a photoreceptor group in a third row and a photoreceptor groupin a fourth row is connected to an electrode terminal 309, and atransfer electrode 16 group in a transverse row which is arranged in theupper side portion of the photoreceptor group in the fourth row isconnected to the electrode terminal 301 again. Such a connectingstructure is repeated. When a voltage is applied to a certain electrodeterminal, the same voltage is applied to all the transfer electrodesconnected to the electrode terminal in the same timing.

In the case in which the image signals (the received charges of thephotoreceptors 11 r, 11 g and 11 b) picked up by each pixel of thesolid-state image capturing device 30 are to be read, a readingpotential (a reading pulse) is applied to each reading gate which is notshown and the received charges (the signal charges) of thephotoreceptors 11 r, 11 g and 11 b are read onto the correspondingtransfer electrode 16 of the vertical CCD register 12 as shown in arrowson the photoreceptors 11 r, 11 g and 11 b.

When a transfer pulse for 9-phase driving is applied to each of theelectrode terminals 301 to 309, the signal charge is transferred in thedirection of the horizontal CCD register 13 and a transfer pulse isapplied to the electrode terminals 25 and 26 of the horizontal CCDregister 13. Consequently, the signal charge is output from an outputsection 14 of the horizontal register 13. Also in the embodiment, anelectrode terminal 28 for the application of an OFD pulse is provided.

FIGS. 3 and 4 are timing charts for explaining the transfer method ofthe vertical CCD register 12. In the drawing, an encircled figurerepresents a last one digit of the designation of each of the electrodeterminals 301 to 309. By cyclically applying a transfer potential (forexample, pulses having a high level (0 V) and a low level (−8 V) to eachelectrode terminal, an electric potential well is moved along thevertical CCD register 12 and signal charges Qi, Qi−1, . . . constitutingthe image signals are transferred to the horizontal register 13. Anoperation timing is the same as that shown in FIG. 21 and FIGS. 3 and 4show a state obtained after a timing t7 in which the sweeping pulse X isended.

In the case in which a high-speed shutter is released, the sweeping iscarried out in a state in which a mechanical shutter is opened asdescribed above. Therefore, a smear charge q enters an electricpotential well in the timing t7 in which the sweeping is ended by thesweeping pulse X. In the timing t7 in which the sweeping is ended, anelectric potential having a high level is applied to electrodes {circlearound (2)}, {circle around (5)} and {circle around (8)} so that theelectric potential well is formed.

In the embodiment, the smear charges in each electric potential wellwhich remain in the timing t7 are collected into one place and thecollected smear charges are transferred and discharged by the verticalCCD register 12 before they are transmitted into the horizontal CCDregister 13 or at the output end of the horizontal CCD register 13.

In the embodiment, all but the electrode □ are set to be electricpotentials having a high level in a timing t700 immediately after thetiming t7. Consequently, the electric potential well is expanded toeight electrodes and three smear charges are united. Subsequently, anelectric potential having a lower level is sequentially applied to theelectrodes {circle around (5)}, {circle around (6)}, {circle around(7)}, {circle around (8)}, {circle around (9)}, {circle around (1)} and{circle around (2)} in timings t701, . . . , t707 to gradually reducethe width of the electric potential well, and three smear charges 3 qare collected into an electric potential well by the electrode {circlearound (5)}.

In a next timing t708, an electric potential having a high level isapplied to the electrodes {circle around (5)}, {circle around (8)} and{circle around (1)} as well as the electrode {circle around (3)} to forman electric potential well for signal charge transfer. In a next readingtiming t709 (corresponding to a reading pulse B2 for a first phase (FIG.21 shows a reading pulse B2 for a second phase)), signal charges Qa, Qb,Qd and Qe of pixels A, B, D and E are read onto the electric potentialwell.

The reading is carried out by applying a reading potential of +16 V to acorresponding reading gate, for example. For this reason, the depth of acorresponding electric potential well for signal charge transfer isgreat. In the timing t708, the electric potential well for signal chargetransfer formed in the position of the electrode {circle around (1)} hasnot been moved to the positions of the pixels C and F. In a timing t709,therefore, the signal charges are not read from the pixels C and F (thesignal charges are read in a timing t8 of the reading pulse B2 for asecond phase which will be described below).

After the signal charges Qa, Qb, Qd and Qe are read, the depth of theelectric potential well is returned to an original depth (a timingt710), and subsequently, the electric potential well is transferred by amethod referred to as accordion transfer. More specifically, in a timingt711, the electrode {circle around (6)} is set to be an electricpotential having a high level and the widths of the electric potentialwells holding the signal charges Qa and Qd are expanded into twoelectrodes respectively, and an electric potential having a low level isapplied to the electrode {circle around (5)} in a next timing t712.Consequently, the widths of the electric potential wells holding thesignal charges Qa and Qd are reduced to one electrode. As a result, theelectric potential wells holding the signal charges Qa and Qd advancecorresponding to one electrode.

In a timing t713, moreover, an electric potential having a high level isapplied to the electrode {circle around (4)} so that the width of theelectric potential well for smear charge transfer is expanded into twoelectrodes. In a next timing t714, an electric potential having a lowlevel is applied to the electrode {circle around (3)} so that the widthof the electric potential well for smear charge transfer is reduced toone electrode. As a result, the electric potential well for smear chargetransfer advances corresponding to one electrode.

Similarly, the processing sequentially proceeds to timings t715 andt716, and an empty electric potential well for signal charge transfer ismoved to the position of the electrode {circle around (2)}. In a nexttiming t8, the reading pulse B2 for a second phase is applied to theelectrode {circle around (2)} so that signal charges Qc and Qf of thepixels C and F are moved from the photoreceptor to the electricpotential well. In a state of a timing t8+Δ immediately after thereading, the depth of a corresponding electric potential well isreturned to an original state and all the signal charges of eachphotoreceptor of the solid-state image capturing device 30 are read ontothe vertical CCD register 12. As shown in timings t801 to t818 in FIGS.3 and 4, each electric potential well for signal charge transfer and anelectric potential well for smear charge transfer are sequentiallytransferred to the horizontal CCD register side, of which descriptionwill be omitted.

Thus, the vertical CCD register 12 of the solid-state image capturingdevice is driven in a multiphase. Consequently, an electric potentialwell which can be used specially for smear charge transfer can beprovided and the smear charges are collectively transferred into theelectric potential well for smear charge transfer. Consequently, thesmear charge can be discharged as will be described below in detail.Thus, it is possible to obtain an excellent image having no smear.

FIG. 5 is a schematic plan view showing a solid-state image capturingdevice according to a second embodiment of the invention. A solid-stateimage capturing device 40 has a structure which is referred to as aso-called honeycomb type, and comprises a photoreceptor group includinga photoreceptor 11 b having a blue filter attached thereto and aphotoreceptor 11 r having a red filter attached thereto which arealternately arranged in a transverse row and a photoreceptor groupincluding the photoreceptor 11 g having the green filter attachedthereto which are alternately arranged in a vertical direction with a ½pitch.

In the drawing, the photoreceptors 11 r, 11 g and 11 b are displayed insquares inclined at 45 degrees. In the solid-state image capturingdevice 40, a transfer electrode 16 is provided along each side of eachsquare of the photoreceptors 11 r, 11 g and 11 b and one transverse rowH1 of the transfer electrode is divided in a channel stop correspondingto each photoreceptor, and the same electric potential is applied to theelectrode group H1 in the transverse row in the same timing.

The solid-state image capturing device 40 according to the embodimentcarries out 8-phase driving. Therefore, the electrode group in eachtransverse row repeats . . . , H7, H8, H1, H2, H3, H4, H5, H6 . . . . Anelectrode terminal 401 is connected to the electrode group H1, anelectrode terminal 402 is connected to the electrode group H2, anelectrode terminal 403 is connected to the electrode group H3, . . . ,and an electrode terminal 408 is connected to the electrode group H8(that is, an electrode group Hx is connected to an electrode terminal 40x).

The transfer electrode 16 provided around each of the photoreceptors 11r, 11 g and 11 b is also arranged in a vertical direction and a transferelectrode group 12 arranged in the vertical direction (only one columnis shown in a dotted line) constitutes a vertical CCD register 12. Whena reading potential (a reading pulse) is applied to a reading gate whichis not shown in order to read image signals picked up by the solid-stateimage capturing device 40 (the received charges of the photoreceptors 11r, 11 g and 11 b), the received charges (signal charges) of thephotoreceptors 11 r, 11 g and 11 b are read onto the correspondingtransfer electrode of the vertical CCD register 12 as shown in an arrowon each of the photoreceptors 11 r, 11 g and 11 b.

A transfer potential (a transfer pulse) is sequentially applied to eachof the electrode terminals 401 to 408 so that a received charge istransferred in a vertical direction (a downward direction in the exampleshown in the drawing) and a signal charge is transferred through atransfer electrode 17 to a horizontal CCD register 13 provided in thelowest stage. The signal charge is transferred in a horizontal directionby the application of the transfer pulse to electrode terminals 25 and26 and is output from an output section 14 of the horizontal register 13as shown in an arrow 27. Moreover, the solid-state image capturingdevice 40 is also provided with an electrode 28 for OFD pulseapplication.

FIG. 6 is a diagram showing the operation timing of the solid-stateimage capturing device according to the second embodiment. FIG. 6 isbasically the same as FIG. 21 except that a detailed pulse waveform (notshown) shown in cross-hatching is different. Also in the embodiment, asignal charge read with a reading pulse B1 is discharged as a dummyoutput and an image signal read with a reading pulse B2 is output for astatic image.

The output for a static image is carried out after a mechanical shutteris closed, and the transfer operation of the vertical CCD register isstopped or is performed at a lower rate than an ordinary reading ratebefore the mechanical shutter is closed (which is the same as in thefirst embodiment). Prior to the reading of a signal charge with thereading pulse B2, electric charges in the vertical CCD register 12 isquickly swept with a sweeping pulse X and electric charges stored in thephotoreceptors 11 r, 11 g and 11 b are zero cleared with an OFD pulse inthe same manner as described above.

FIG. 7 is a timing chart for explaining the transfer method of thesolid-state image capturing device according to the second embodiment.In the drawing, the encircled numbers represent the last ones digit ofeach of the electrode terminals 401 to 408. Moreover, pixels A, B, C andD represent photoreceptors in odd-numbered rows in FIG. 5 which areadjacent to the vertical CCD register 12, and similarly, pixels E, F, Gand H represent photoreceptors in even-numbered rows of FIG. 5.

In the embodiment, signal charges Qa, Qb, Qc and Qd of the pixels A, B,C and D in the odd-numbered rows (the photoreceptors 11 r and 11 b forblue and red colors in FIG. 5) are read and transferred onto an electricpotential well formed in the vertical CCD register 12 in theeven-numbered column (since the vertical CCD register 12 in FIG. 5 isprovided in a third column, both sides are second and fourth columns),and signal charges Qe, Qf, Qg and Qh of pixels E, F, G and H in theeven-numbered rows (the photoreceptor 11 g for a green color in FIG. 5)are read and transferred onto the vertical CCD register 12 in theodd-numbered column.

In each timing shown in FIG. 7, the timing chart of the electricpotential well transferred through the vertical CCD register in theeven-numbered column is shown in each upper stage and the timing chartof the electric potential well transferred through the vertical CCDregister in the odd-numbered column is shown in each lower stage.

Also in the solid-state image capturing device 40 according to theembodiment, smear charges remaining at the end point of a sweeping pulseX are collected into one electric potential well and only the collectedsmear charges are transferred separately from the signal charge and arefinally cancelled. Consequently, an image having no smear is obtained.More specifically, in the embodiment, a smear charge q remaining in anend timing t7 of the sweeping pulse X is collected into an electricpotential well corresponding to one electrode by first setting all butthe electrode {circle around (4)} to an electric potential having a highlevel (a timing ta), collecting them every two smear charges 2 q andthen applying an electric potential having a low level to the electrodes{circle around (5)}, {circle around (6)}, {circle around (7)}, . . . inthis order (a timing tb).

In the same manner as in the first embodiment, an electric potentialwell for signal charge transfer is formed (not shown) and the signalcharges of the pixels A, B, C and D are read, and the accordion transferis started by each vertical CCD register from a timing t8+Δ. Morespecifically, the electrodes {circle around (6)} and {circle around (7)}are set to have a high level in a timing tc, thereby increasing thewidth of a corresponding electric potential well, and the electrodes{circle around (5)} and {circle around (6)} are sequentially set to havea low level in a timing td, thereby reducing the width of acorresponding electric potential well into one electrode. As a result,the electric potential well is caused to advance corresponding to twoelectrodes.

Thus, the electric potential well transfer of each of the vertical CCDregisters 12 in the even-numbered and odd-numbered columns is caused toprogress at the same time. When an empty electric potential well forsignal charge transfer in the odd-numbered column comes to the positionsof the pixels E, F, G and H, the signal charges Qe, Qf, Qg and Qh of thepixels E, F, G and H are read and the transfer of each vertical CCDregister 12 is started again (a timing tg).

Consequently, the signal charges of photoreceptor groups correspondingto two rows in the transfer electrode group in a transverse row shown inFIG. 5 are transferred, and the signal processing section 35 shown inFIG. 1 can fetch the image signals of colors R, G and B together and canbe subjected to an image processing. Similarly, the smear charges arealso transferred in a transfer electrode group in a transverse row.Therefore, only the smear charge can be discharged together as will bedescribed below.

FIG. 8 is a timing chart for explaining the transfer method of asolid-state image capturing device according to a third embodiment ofthe invention. The structure of the solid-state image capturing deviceaccording to the third embodiment is the same as that of the secondembodiment shown in FIG. 5. While the second embodiment provides aprogressive scanning type in which a signal charge is read from allpixels, the third embodiment provides an interlace scanning type. Alsoin this case, however, the smear charges are collected into one electricpotential well and are thus transferred, and finally, are cancelled inthe same manner.

More specifically, a smear charge q remaining in the end point (a timingt7) of the sweeping pulse X is collected into an electric potential wellcorresponding to two electrodes (a timing tb). Then, an electricpotential well for signal charge transfer is formed and signal chargesQa and Qc of pixels A and C are read, and all the electric potentialwells are caused to advance in the direction of a horizontal CCDregister at the same time.

Because of the interlace scanning type, there is a space for twoelectrodes between the electric potential wells. For example, referringto the electric potential well of the signal charge Qa formed by settingthe electrodes {circle around (1)} and {circle around (2)} in the timingt8+Δ to have a high level, the electrode {circle around (3)} is set tohave a high level, and at the same time, the electrode {circle around(1)} is set to have a low level so that an electric potential wellhaving a width corresponding to two electrodes can be caused to advancefor one electrode. An electric potential well holding an adjacent smearcharge 2 q can also be caused to advance for one electrode at the sametime. Consequently, the transfer can be carried out at a higher speedthan that in the second embodiment.

Since the interlace scanning type is used in the embodiment, the numberof read pixels in a vertical direction is ½ of that of the progressivescanning type and a resolution in the vertical direction isdeteriorated. The width of the electric potential well for transferringthe signal charge can be taken for two electrodes. Therefore, the amountof saturation of the signal charge is doubled as compared with thesecond embodiment in which a signal charge is transferred through anelectric potential well for one electrode. Thus, it is possible toobtain an advantage that a wide dynamic range can be obtained.

While a high-speed shutter is released by an electronic shutter in eachof the embodiments, the invention can also be applied to the case inwhich a low-speed shutter is released by the electronic shutterfunction. In a digital still camera mounting a mechanical shutter,however, it is desirable that the low-speed shutter should be releasedby the mechanical shutter. In this case, it is preferable that the sametransfer pulse as transfer pulses for first to fourth phases should beapplied to electrode terminals for fifth to eighth phases of thevertical CCD register and only a signal charge should be transferredwithout generating an electric potential well for a smear charge.Consequently, it is possible to obtain an image of high picture qualitywhen releasing the low-speed shutter.

FIG. 9 is a schematic plan view showing a solid-state image capturingdevice according to a fourth embodiment of the invention. A solid-stateimage capturing device 200 is almost the same as the solid-state imagecapturing device 40 (FIG. 5) according to the second embodiment exceptthat the number of electrode terminals to which a transfer potential isapplied and a connecting structure thereof are different.

In the embodiment, 16 electrode terminals 201 to 216 are provided forapplying a transfer potential to a vertical CCD register 12 in order to16-phase drive the vertical CCD register 12 and are connected toelectrode groups H1 to H16 in a horizontal line, respectively. Theelectrode terminals 201 to 216 are connected to the electrode groups H1to H16 in which the last two digits of the designations (figures) of theelectrode terminals are coincident with figures after “H”.

FIG. 10 is a timing chart for explaining a transfer method in thesolid-state image capturing device according to the fourth embodiment.In the second embodiment described with reference to FIG. 7, the widthof the electric potential well for transferring a signal charge is setto one electrode. For this reason, the amount of saturation of thesignal charge is a half of that in the third embodiment (FIG. 8). On theother hand, the fourth embodiment is characterized in that a progressivescanning type is used and the width of the electric potential well forsignal charge transfer is set to two-electrodes.

Also in the embodiment, smear charges remaining in each electricpotential well in the end point (a timing t7) of a sweeping pulse X arecollected into one electric potential well (a timing tb). As describedabove, in order to increase the amount of saturation of the signalcharge, the width of the electric potential well for signal chargetransfer is set to two electrodes and an electric potential welldedicated to smear charge transfer has a width of one electrode.Differently from the second embodiment, the electric potential well forsignal charge transfer and the electric potential well for smear chargetransfer are transferred through accordion transfer and the width of theelectric potential well for signal charge transfer can be maintainedcorresponding to two electrodes during the transfer. Other respects arethe same as in the second embodiment.

According to the embodiment, an image having a high resolution isobtained because of the progressive scanning type. In addition, thesignal charge is transferred through the electric potential well for twoelectrodes to be the electric potential well for signal charge transfer.Consequently, it is possible to obtain an image having a wide dynamicrange.

FIG. 11 is a schematic plan view showing a solid-state image capturingdevice according to a fifth embodiment of the invention. A solid-stateimage capturing device 500 is almost the same as the solid-state imagecapturing device 200 (FIG. 9) according to the fourth embodiment exceptthat the number of electrode terminals for applying a transfer potentialand a connecting structure thereof are different.

In the embodiment, 12 electrode terminals 501 to 512 are provided forapplying a transfer potential to a vertical CCD register 12 in order to12-phase drive the vertical CCD register 12 and are connected toelectrode groups H1 to H2 in a horizontal line, respectively. Theelectrode terminals 501 to 512 are connected to the electrode groups H1to H12 in which the last two digits of the designations (figures) of theelectrode terminals are coincident with figures after “H”.

FIGS. 12 and 13 are timing charts for explaining a transfer method inthe solid-state image capturing device according to the fifthembodiment. The fifth embodiment is basically the same as the fourthembodiment described with reference to FIG. 10, and the width of anelectric potential well for smear charge transfer corresponds to oneelectrode and the width of an electric potential well for signal chargetransfer corresponds to two electrodes, and progressive scanning forreading and transferring the signal charges of all pixels is carriedout. The fifth embodiment is different from the fourth embodiment inthat the numbers of the electrode terminals are different from eachother. For this reason, the number of pins to be provided in thesolid-state image capturing device is decreased and a transfer pulse canbe created easily.

According to the embodiment, an image having a high resolution isobtained because of the progressive scanning type. In addition, thesignal charge is transferred through the electric potential well for twoelectrodes to be the electric potential well for signal charge transfer.Consequently, it is possible to obtain an advantage that an image has awide dynamic range, and furthermore, a transfer pulse can be createdeasily and the number of the pins of the solid-state image capturingdevice is decreased.

FIG. 14 is a diagram showing the structure of a digital still cameraaccording to another embodiment of the invention. Differently from thedigital still camera according to the embodiment shown in FIG. 1, animage synthesizing section 35 e is provided in a signal processingsection 35 and a plurality of image signals which have been subjected toa static image processing are synthesized. For the solid-state imagecapturing device 30 to be mounted on the digital still camera, any ofthe solid-state image capturing devices according to the embodiments maybe used.

In the digital still camera according to the embodiment, it is possibleto select a high-speed photographing mode for outputting a static imageby the single photographing of a high-speed shutter, a low-speedphotographing mode for outputting a static image by single photographingusing a mechanical shutter, and furthermore, a synthetic photographingmode for synthesizing and outputting a static image photographed by thehigh-speed shutter and a static image photographed by the low-speedshutter continuously therewith.

FIG. 15 is a diagram showing an operation timing in the syntheticphotographing mode. A processing of draining the stored charges of aphotoreceptor group with an OFD pulse and a processing of sweeping thestored charges of a vertical CCD register with a sweeping pulse X arethe same as those of the embodiments described above. Also in theembodiment, a signal charge read from the solid-state image capturingdevice with a reading pulse B1 is discharged as a dummy output.

A signal charge photographed by the high-speed shutter is read with areading pulse B2 after the OFD pulse, and is transferred through thevertical CCD register 12 and the horizontal CCD register 13 as describedin each of the embodiments, and is output as a high-speed shutter staticimage S1 to the signal processing section 35 (FIG. 14) after a nextvertical blanking signal A2.

While a signal charge is read from a photoreceptor onto the vertical CCDregister 12 by the high-speed shutter and a mechanical shutter is thenclosed, the signal charge stored in the photoreceptor is read with areading pulse B3 generated in a next vertical blanking signal A3 and istransferred in the same manner, and is output as a low-speed shutterstatic image S2 to the signal processing section 35. The signalprocessing section 35 synthesizes these two static images S1 and S2 bythe synthesizing section 35 e and processes them by a common signalprocessing section 35 d, and is then stored in a recording section 36and is displayed on a display section 37. The static images thussynthesized have a wide dynamic range.

FIG. 16 is a view for explaining a structure in which a smear chargetransferred immediately before a horizontal CCD register 13 isdischarged as described above, and FIG. 16( a) is a plan view showing asolid-state image capturing device, illustrating the details of thevicinity of the horizontal CCD register 13 in FIG. 2, for example. Inthis example, a second transfer electrode 16 from the horizontal CCDregister 13 is provided with a smear charge discharging structure. Thesmear charge discharging structure is provided in all the secondtransfer electrodes 16 in a transverse row from the horizontal CCDregister 13 shown in FIG. 2.

FIG. 16( b) is a sectional view taken along a line B-B in FIG. 16( a). AP well 710 is provided on the surface side of an n-type semiconductorsubstrate 700 of the solid-state image capturing device, and a buriedchannel 708 comprising an n-type semiconductor layer is formed on thesurface of the P well 710. An electric charge is stored in andtransferred to the buried channel 708, and a channel stop region 707 isprovided adjacently to the buried channel 708 in order to divide anadjacent vertical CCD register 12 from the buried channel 708.

A gate insulating film 711 is provided on the surface of the P well 710,and the transfer electrode 16 formed of polysilicon is provided on theburied channel 708 through the gate insulating film 711. A drain 706 isprovided on the surface of the P well 710 in a position placed slightlyapart from the buried channel 708, and the drain 706 and thesemiconductor substrate 700 are connected to each other through a drainconnecting region 709.

A control electrode 705 for smear charge discharge which is formed ofpolysilicon is provided between the buried channel 708 and the drain 706through the gate insulating film 711. The transfer electrode 16 and thecontrol electrode 705 are covered with an insulating film 712, a lightshielding film 715 is provided thereon, and furthermore, an insulatingfilm 713 is provided thereon and a transparent film 714 is provided asan uppermost layer.

With such a structure, when a smear charge is transferred to thetransfer electrode 16 juxtaposed with the control electrode 705, acontrol voltage is applied to the control electrode 705 so that a smearcharge stored between the transfer electrode 16 and the buried channel708 provided thereunder is transferred to the drain 706 and isdischarged to the semiconductor substrate 700.

FIG. 17 is a view showing an example in which the smear chargedischarging structure is provided at the end of the horizontal CCDregister 13 on the opposite side of the vertical CCD register 12. A Pwell 801 is provided on the surface side of an n-type semiconductorsubstrate 800, and a buried channel 802 and a drain 803 are provided onthe surface of the P well 801. A gate insulating film 804 is provided onthe surface of the P well 801, and a transfer electrode 805 for thehorizontal CCD register is provided above the buried channel 802 throughthe gate insulating film 804 and a control electrode 806 for smearcharge discharge is provided above a portion between the buried channel802 and the drain 803.

The transfer electrode 805 and the control electrode 806 are coveredwith an insulating film 807, a light shielding film 808 is providedthereon, and furthermore, an insulating film 809 is provided thereon anda transparent film 810 is provided as an uppermost layer.

With such a structure, when the smear charge is transferred between thetransfer electrode 805 and the buried channel 802 provided thereunder, acontrol voltage is applied to the control electrode 806 so that thesmear charge is transferred to the drain 803 and is thus discharged.

According to each of the embodiments described above, the smear chargesin the vertical CCD register are swept with a sweeping pulse and thesmear charges entering the transfer electrode are then collected andtransferred through a special electric potential well, and are thusdischarged. Therefore, it is possible to obtain an excellent imagehaving no deterioration in picture quality which is caused by smear.

As described above, in the case in which a high-speed shutter isreleased by an electronic shutter, the transfer of the vertical registeris carried out with a mechanical shutter opened. Therefore, it isnecessary to collectively transfer and discharge the smear charges. Inthe case in which a low-speed shutter is released by the mechanicalshutter, however, the transfer of the vertical register is carried outwith the mechanical shutter closed. Therefore, the surface of thesolid-state image capturing device is not exposed to outside light andthe smear charge does not need to be transferred and discharged.

For this reason, in the digital still camera, it is possible to select ahigh-speed photographing mode in which smear charges are collected,transferred and discharged and a low-speed photographing mode in whichthe smear charges are neither collected, transferred nor dischargedaccording to the embodiments, and it is preferable that any of the modesshould be selected to capturing the image of an object. In this case,the mode may be selected manually or automatically interlockingly withthe operation of the mechanical shutter.

Moreover, while the description has been given by taking the interlinetransfer type CCD area image sensor as an example in the embodiments,the invention can also be applied to a frame interline transfer type CCDarea image sensor. Furthermore, while the smear charge is discharged ata vertical register end or a horizontal register output end in theembodiments, a voltage signal by the smear charge may be exactly outputfrom the solid-state image capturing device and may be canceled in thesignal processing section.

According to the invention, it is possible to output an excellent imagehaving no deterioration in picture quality which is caused by smear.

1. A solid-state image capturing device, comprising: a pixel arrayarranged in a row direction and a column direction orthogonal thereto; avertical register having a plurality of transfer electrodes used to readsignal charges that are generated in respective pixels when therespective pixels receive light, the vertical register that sequentiallytransfers the signal charges in the column direction upon receipt of atransfer pulse; a horizontal register that receives the signal chargestransferred by the vertical register and transfers the signal charges ina horizontal direction; a smear drain structure that is placed slightlyapart from the vertical register, wherein the vertical register and thesmear drain structure are disposed on one side of the horizontalregister in the column direction; an output section that outputs thesignal charges transferred by the horizontal register; a control sectionthat generates first electronic potential wells and applies a certaintransfer pulse to the plurality of transfer electrode to collect smearcharges that are generated in the vertical register into the firstelectronic potential wells, wherein the control section causes thevertical register and the smear drain structure to transfer the firstelectronic potential wells, in which the smear charges are collected, tothe smear drain structure, and the smear drain structure discharges thetransferred smear charges.
 2. The solid-state image capturing deviceaccording to claim 1, wherein the smear drain structure is placedimmediately before the horizontal register in the column direction. 3.The solid-state image capturing device according to claim 1, wherein atleast one of the transfer electrodes is disposed between the horizontalregister and a transfer electrode adjacent, in the row direction, to thesmear drain structure.
 4. The solid-state image capturing deviceaccording to claim 1, wherein the vertical register further includes achannel below the transfer electrodes, the signal charges and the smearcharges are transferred in the channel in the column direction, thesmear drain structure includes a drain and a gate electrode that isdisposed above at least a position between the channel of the verticalregister and the drain.
 5. The solid-state image capturing deviceaccording to claim 4, wherein the control section applies anothercertain transfer pulse to the plurality of transfer electrodes totransfer the first electric potential wells, in which the smear chargesare collected, to a transfer electrode adjacent to the smear drainstructure in the row direction, the control section applies furtheranother certain transfer pulse to the gate electrode of the smear drainstructure to transfer the smear charges from the adjacent transferelectrode to the drain, and the smear charges transferred to the drainare discharged to a substrate.
 6. The solid-state image capturing deviceaccording to claim 1, wherein the control section applies the certaintransfer pulse to the plurality of transfer electrode to collect thesmear charges into the first electronic potential wells before thesignal charges are read from the respective pixels to the verticalregister, the control section generates second electronic potentialwells after the smear charges are collected into the first electronicpotential wells and applies another certain transfer pulse to thetransfer electrodes to transfer the signal charges from the respectivepixels to the second electronic potential wells, and the firstelectronic potential wells and the second electronic potential wells areconcurrently transferred to the horizontal register without mixing thesmear charges with the signal charges.
 7. A solid-state image capturingdevice, comprising: a pixel array arranged in a row direction and acolumn direction orthogonal thereto; a vertical register having aplurality of transfer electrodes used to read signal charges that aregenerated in respective pixels when the respective pixels receive light,the vertical register that sequentially transfers the signal charges inthe column direction upon receipt of a transfer pulse; a horizontalregister that receives the signal charges transferred by the verticalregister and transfers the signal charges in a horizontal direction; asmear drain structure that is placed across the horizontal register fromthe vertical register; an output section that outputs the signal chargestransferred by the horizontal register; a control section that generatesfirst electronic potential wells and applies a certain transfer pulse tothe plurality of transfer electrode to collect smear charges that aregenerated in the vertical register into the first electronic potentialwells, wherein the control section causes the vertical register, thehorizontal register and the smear drain structure to transfer the firstelectronic potential wells, in which the smear charges are collected, tothe smear drain structure, and the smear drain structure discharges thetransferred smear charges.
 8. The solid-state image capturing deviceaccording to claim 7, wherein the smear drain structure is placed at anend of the horizontal register.
 9. The solid-state image capturingdevice according to claim 7, wherein the smear drain structure includesa drain and a gate electrode that is disposed above at least a positionbetween the horizontal register and the drain.
 10. The solid-state imagecapturing device according to claim 9, wherein the control sectionapplies another certain transfer pulse to the plurality of transferelectrodes to transfer the first electric potential wells, in which thesmear charges are collected, to the horizontal register, the controlsection applies further another certain transfer pulse to the gateelectrode of the smear drain structure to transfer the smear chargesfrom the horizontal register to the drain, and the smear chargestransferred to the drain are discharged to a substrate.
 11. Thesolid-state image capturing device according to claim 7, wherein thecontrol section applies the certain transfer pulse to the plurality oftransfer electrode to collect the smear charges into the firstelectronic potential wells before the signal charges are read from therespective pixels to the vertical register, the control sectiongenerates second electronic potential wells after the smear charges arecollected into the first electronic potential wells and applies anothercertain transfer pulse to the transfer electrodes to transfer the signalcharges from the respective pixels to the second electronic potentialwells, and the first electronic potential wells and the secondelectronic potential wells are concurrently transferred to thehorizontal register without mixing the smear charges with the signalcharges.
 12. A solid-state image capturing device, comprising: a pixelarray arranged in a row direction and a column direction orthogonalthereto; a vertical register having a plurality of transfer electrodesused to read signal charges that are generated in respective pixels whenthe respective pixels receive light, the vertical register thatsequentially transfers the signal charges in the column direction uponreceipt of a transfer pulse; a horizontal register that receives thesignal charges transferred by the vertical register and transfers thesignal charges in the row direction; an output section that outputs thesignal charges transferred by the horizontal register; and a drivingsection that generates groups of first electric potential wells, andapplies a certain transfer pulse to the plurality of transfer electrodesto collect smear charges in each group into one first electric potentialwell, wherein, the driving section causes the vertical register thefirst electronic potential wells, in which the smear charges arecollected, the solid-state image capturing device further comprisingsmear drain means for discharging the transferred smear charges.
 13. Thesolid-state image capturing device according to claim 12 wherein thedriving section applies the certain transfer pulse to the plurality oftransfer electrode to collect the smear charges in each group into theone first electronic potential well before the signal charges are readfrom the respective pixels to the vertical register, the driving sectiongenerates second electronic potential wells after the smear charges ineach group are collected into the one first electronic potential welland applies another certain transfer pulse to the transfer electrodes totransfer the signal charges from the respective pixels to the secondelectronic potential wells, and the first electronic potential wells andthe second electronic potential wells are concurrently transferred tothe horizontal register without mixing the smear charges with the signalcharges.